1. Field of the Invention
Applicants"" invention relates to a circulator device that is isolated from the environment. More particularly, it relates to a circulator with a wrapped foil ground and a sealed cover that allows the exterior of the circulator to be washed without damaging the function of the circulator.
2. Background Information
Ferrite devices have been well known since the mid-1900s. The term xe2x80x9cferritexe2x80x9d means xe2x80x9cironlikexe2x80x9d in that a ferrite material has magnetic properties, although ferrites are a class of ceramic material. The first work with ferrite materials was done in the late 1940s. Since that time, many ferrite devices have been developed and are found in a variety of applications including refrigerator doors, tape recording heads, a.m. radio antennas, and microwave applications. Although many of the ferrite devices have a fairly simply configuration, consisting typically of ferrite material and magnet(s) in a metallic structure, ferrite devices abound with subtleties.
One of the most useful ferrite devices, the junction circulator, was developed in the late 1950s. A circulator is a microwave coupling device having three or more terminals that provides for energy entering a first terminal to be transmitted to the next adjacent terminal in a specific direction. Thus, in a three-port circulator, the junction circulator takes energy incident on port 1 and xe2x80x9ccirculatesxe2x80x9d it to port 2, energy incident on port 2 exists via port 3 and energy incident on port 3 exits port 1. If port 3 is terminated by introducing material that absorbs energy, an isolator is produced. Thus, energy is passed from port 1 to port 2, but returning energy is circulated to port 3 where it is absorbed, and thus the source is xe2x80x9cisolatedxe2x80x9d from the load. Circulator junctions may be combined in numbers greater than three, for example, the four port circulator. Circulators and isolators are the most common microwave ferrite devices and are found in many applications including radar and satellite.
Two of the most common kinds of ferrite devices are the circulator and the isolator. A circulator is a three or more port device which xe2x80x9ccirculatesxe2x80x9d microwave energy from port to port. For example, in a three port circulator, energy is circulated from port 1 to 2, 2 to 3, and 3 to 1. An isolator is a three port circulator with an energy absorbing xe2x80x9cloadxe2x80x9d connected to port 3. xe2x80x9cCirculationxe2x80x9d is accomplished by routing microwave energy through a magnetized ferrite material. The material is a ceramic with magnetic properties, and is generally fired in a kiln like other ceramics. Circulators are commonly used in microwave radios (and other microwave systems) to absorb reflected energy protecting amplifiers and other circuit functions. A circulator is used in xe2x80x9cduplexingxe2x80x9d a transmitter and a receiver such that they can share the same antenna. For example, the transmitter is connected to port 1, the antenna to port 2, and the receiver to port 3.
The general structure of a circulator includes a circuit sandwiched between a top ferrite and a bottom ferrite with a magnet above the top ferrite and a cover. The top and bottom ferrites must be grounded to one another. Three traditional methods exist for grounding the top and bottom ferrite disks. In the first, two steel plates, a top and a bottom, are added to either side of the top ferrite and the bottom ferrite. The steel plates are in contact with the ferrite disks and are grounded to one another by use of screws between the two steel plates. The screws also act to hold the assembly together. In this configuration, the magnet may also be used as a grounding path because it is generally plated. The problem with this design is that the magnets do not always touch the top steel plate. Also, the screws tend to be a poor grounding path. If the threads of the steel plates or the screws get stripped, they will not have good contact and thus give poor grounding.
A second traditional design uses the cover as a grounding path. In this assembly, a grounding disk in contact with the top ferrite contacts the side walls of the steel cover which in turn contacts a steel baseplate which is in contact with the bottom ferrite. This design is easy to build, but relies on the steel cover to provide the grounding path to the top of the ferrite to the bottom. If the grounding disk does not touch the sides, the grounding path is lost. Additionally, this design also increases the distance of the grounding path.
A third design is similar to the second in that a cover is used to create a grounding path. However, the third design a full cover is used rather than a grounding disk and sidewalls attached to a baseplate. In the third traditional assembly, a full cover is attached about the ferrite assembly to a baseplate. This type of assembly has the same problems as the second.
In current, conventional circuit board production methods, the circuit board is constructed and then washed after completion in order to remove foreign matter from the circuit board. This washing can damage the circulator. Additionally, once the circuit board and attached circulator are in use, environmental moisture may come in contact with both, further providing the chance for damage to the circulator.
Thus, there is a need for a circulator device that functions as a traditional circulator, but is insulated from the environment in order that moisture cannot damage the circulator. Further, it is advantageous to decrease the distance of the grounding path of the circulator assembly.
The present invention provides for a grounded circulator that is isolated from the environment.
The present invention provides a novel apparatus that will allow circuit board manufacturers to wash the circuit board upon completion without damaging the circulators. The present invention further provides:
a. A reduction in the grounding pathway distance;
b. A circulator assembly that assures ground contact between the top and bottom ferrites;
c. A highly conductive, grounding path material;
d. A grounded circuit assemble that is easily manufactured;
e. A grounding pathway that does not require touching the sides of the steel cover or use of screws; and
f. A baseplate with notches shaped to accept an insert having either a hole to run the circuit tab through and an embedded microstrip to contact the circuit tab.
In order to solve the difficulties presented in attempting to obtain these features, an improved insulated circulator apparatus has been developed which isolates the grounded circuit assembly within a sealed, insulating cover.
Specifically, the present invention provides for a grounded circuit assembly which is comprised of two ferrite disks sandwiching a circuit, and wrapped with a grounding foil. Other components of the circulator, such as the pole piece and magnet, can be placed either within the grounding foil wrap or outside the grounding foil wrap and the entire grounded circuit assembly and additional components are sealed with an insulating cover attached to a baseplate. The baseplate has a plurality of notches corresponding with the number of circuit tabs of the circuit. The circuit tabs extend to the notches. Inserts are placed in the notices than can have either a hole through which the circuit tab can be extended, or a microstrip may be embedded through the insert. If the insert has a hole and the circuit tab is placed within the hole, a sealing material may be used in the hole to maintain the insulated integrity of the circulator. In either embodiment, the inserts allow communication between the circulator and other electronic sources or components while keeping the interior of the circulator, including the grounded circuit assembly, isolated from the environment and moisture.